Ultraviolet-Initiated In-Situ Cross-Linking of Multifunctional Binder Backbones Enables Robust Lithium-Sulfur Batteries

Abstract

Lithium-sulfur (Li-S) batteries show attractive prospects owing to their high theoretical energy density, but their commercialization still faces such challenges as lithium polysulfides shuttling, severe volume change and considerable polarization. These stubborn issues place higher demands on each component in the battery, such as the development of multifunctional binders with superior mechanical properties. Herein, ethoxylated trimethylolpropane triacrylate was firstly introduced into sulfur cathodes, and in-situ cross-linked by ultraviolet (UV) curing combined with traditional polyvinylidene difluoride binder (i.e., forming a binary binder, denoted as c-ETPTA/PVDF) to construct high-loading and durable Li-S batteries. The covalently cross-linked ETPTA framework not only significantly enhances the mechanical strength of the laminate, but also offers a strong chemical affinity for lithium polysulfides due to the abundant oxygen-containing groups. Moreover, the moderate interaction force between ether oxygen bonds and Li⁺ further accelerates the Li⁺ transport. As such, the S-c-ETPTA/PVDF electrode exhibited an ultralow attenuation rate of 0.038% at 2 C over 1000 cycles. Even under a sulfur loading of 7.8 mg_S·cm^-2, an average areal capacity of 6.2 mAh·cm^-2 could be achieved after 50 cycles. This work indicates that light-assisted curing technology holds great promise in the fabrication of robust and high-energy-density Li-S batteries.

Keywords

Lithium-sulfur batteries / Ultraviolet curing / In-situ cross-linked / Multifunctional binder / High-strength electrode

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